[PATCH 1/4] ACPI/IORT: Check ATS capability in root complex nodes

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

Root complex node in IORT has a bit telling whether it supports ATS or
not. Store this bit in the IOMMU fwspec when setting up a device, so it
can be accessed later by an IOMMU driver.

Use the negative version (NO_ATS) at the moment because it's not clear
if/how the bit needs to be integrated in other firmware descriptions. The
SMMU has a feature bit telling if it supports ATS, which might be
sufficient in most systems for deciding whether or not we should enable
the ATS capability in endpoints.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
---
 drivers/acpi/arm64/iort.c | 11 +++++++++++
 include/linux/iommu.h     |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index e48894e002ba..7f2c1c9c6b38 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -1028,6 +1028,14 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size)
 	dev_dbg(dev, "dma_pfn_offset(%#08llx)\n", offset);
 }
 
+static bool iort_pci_rc_supports_ats(struct acpi_iort_node *node)
+{
+	struct acpi_iort_root_complex *pci_rc;
+
+	pci_rc = (struct acpi_iort_root_complex *)node->node_data;
+	return pci_rc->ats_attribute & ACPI_IORT_ATS_SUPPORTED;
+}
+
 /**
  * iort_iommu_configure - Set-up IOMMU configuration for a device.
  *
@@ -1063,6 +1071,9 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
 		info.node = node;
 		err = pci_for_each_dma_alias(to_pci_dev(dev),
 					     iort_pci_iommu_init, &info);
+
+		if (!err && !iort_pci_rc_supports_ats(node))
+			dev->iommu_fwspec->flags |= IOMMU_FWSPEC_PCI_NO_ATS;
 	} else {
 		int i = 0;
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 3dbeb457fb16..ed6738c358ca 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -509,10 +509,14 @@ struct iommu_fwspec {
 	const struct iommu_ops	*ops;
 	struct fwnode_handle	*iommu_fwnode;
 	void			*iommu_priv;
+	u32			flags;
 	unsigned int		num_ids;
 	u32			ids[1];
 };
 
+/* Firmware disabled ATS in the root complex */
+#define IOMMU_FWSPEC_PCI_NO_ATS			(1 << 0)
+
 int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
 		      const struct iommu_ops *ops);
 void iommu_fwspec_free(struct device *dev);
-- 
2.21.0